Indiana County’s seasonally adjusted unemployment rate rose six-tenths of a percentage point in September to 8.5 percent.

It was the largest monthly increase since October 1998, and pushed the rate to its highest level since November 1995, according to the Pennsylvania Department of Labor and Industry.

The county’s jobless rate was below those of Pennsylvania (8.8 percent) and the nation (9.8 percent), as it has been for 13 consecutive months.

Indiana County’s unemployment rate was up 3 percentage points since last September, the largest over-the-year increase in more than 25 years.

In September, a gain of 600 people pushed the county’s civilian labor force to a record high of 47,900. The number of employed people grew by 200 to 43,800, and the number of unemployed residents increased by 400 to 4,100.

Unemployment rates for Pennsylvania’s 67 counties ranged from 6.1 percent in Centre County to 17 percent in Cameron County.